Electron beam recorder and electron beam irradiation position detecting method

ABSTRACT

An electron beam recorder includes an electron optical system for irradiating an electron beam on a master of an information recording medium and an electron beam irradiation position detecting unit for detecting an irradiation position of the electron beam in the electron optical system while the electron beam is being irradiated on the master by the electron optical system.

This application is a Divisional of U.S. patent application Ser. No.10/784,391 filed Feb. 23, 2004 the entire disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to electron beam recorders andelectron beam irradiation position detecting methods and moreparticularly, to an electron beam recorder and an electron beamirradiation position detecting method, in which signals are spirallyrecorded on a master of an information rerecording medium such as anoptical disc highly accurately.

2. Description of the Prior Art

In general, manufacture an optical disc includes a step in which byusing an optical disc master recorder employing a laser or an electronbeam as a light source, a master coated with photoresist is exposed anddeveloped such that an optical disc master formed, on its surface, withconcave and convex patterns such as information pits and grooves isproduced, a step of producing a metallic die which has the concave andconvex patterns transferred thereto from the optical disc master and iscalled a “stamper”, a step of producing a resinous molded substrate byusing the stamper and a step in which a recording film, a reflectivefilm, etc. are formed on the molded substrate so as to be bonded to oneanother.

An electron beam recorder used for exposure at the time an optical discmaster is produced by using an electron beam is generally arranged asfollows. FIG. 15 shows an arrangement of a conventional electron beamrecorder. The conventional electron beam recorder includes an electronbeam source 1101 for generating an electron beam 1120 and an electronoptical system 1102 which converges the emitted electron beam 1120 ontoa resist master 1109 so as to record information patterns on the resistmaster 1109 in accordance with inputted information signals. Theelectron beam source 1101 and the electron optical system 1102 areaccommodated in a vacuum chamber 1113.

The electron beam source 1101 is constituted by a filament for emittingelectrons upon flow of electric current therethrough, an electrode fortrapping the emitted electrons, an electrode for extracting andaccelerating the electron beam 1120, etc. and is adapted to emit theelectrons from one point.

Meanwhile, the electron optical system 1102 includes a lens 1103 forconverging the electron beam 1120, an aperture 1104 for determining abeam diameter of the electron beam 1120, electrodes 1105 and 1106 fordeflecting the electron beam 1120 in orthogonal directions, respectivelyin accordance with the inputted information signals, a shielding plate1107 for shielding the electron beam 1120 bent by the electrode 1105 anda lens 1108 for converging the electron beam 1120 onto a surface of theresist master 1109.

Furthermore, the resist master 1109 is held on a rotary stage 1110 andis moved horizontally together with the rotary stage 1110 by ahorizontally traveling stage 1111. If the master 1109 is movedhorizontally by the horizontally traveling stage 1111 while beingrotated by the rotary stage 1110, the electron beam 1120 can beirradiated spirally on the master 1109 so as to record the informationsignals of the optical disc spirally on the master 1109.

Moreover, a focusing grid 1112 is provided so as to be substantiallyflush with the surface of the master 1109. This focusing grid 1112 isprovided for adjusting a focal position of the lens 1108 such that thelens 1108 converges the electron beam 1120 onto the surface of themaster 1109. If electrons reflected by the focusing grid 1112 orsecondary electrons emitted from the focusing grid 1112 upon irradiationof the electron beam 1120 on the focusing grid 1112 are detected by adetector such that a grid image is monitored, the focal position of thelens 1108 can be adjusted from a state in which the grid image is seen.

The electrode 1105 is provided for bending the electron beam 1120 in adirection substantially perpendicular to a feed direction of thehorizontally traveling stage 1111. Since the electrode 1105 bends theelectron beam 1120 towards the shielding plate 1107 in accordance withsignals inputted to the electrode 1105, the electrode 1105 is capable ofselecting whether or not the electron beam 1120 is irradiated on themaster 1109 such that information pit patterns are recorded on themaster 1109.

Meanwhile, the electrode 1106 is provided for bending the electron beam1120 in a direction substantially perpendicular to that of the electrode1105, namely, in the substantially same direction as the feed directionof the horizontally traveling stage 1111 and is capable of bending theelectron beam 1120 in the substantially same direction as the feeddirection of the horizontally traveling stage 1111 in accordance withsignals inputted to the electrode 1106. The feed direction of thehorizontally traveling stage 1111 corresponds to a radial direction ofthe master 1109 to be recorded. Variations of a track pitch of theoptical disc, etc. can be corrected by the signals inputted to theelectrode 1106.

In the optical disc, since the track pitch of information signals to berecorded is required to be recorded highly accurately, feed amount ofthe horizontally traveling stage 1111, nonrepeatable runout of therotary stage 1110 or variations of irradiation position of the electronbeam 1120 should be controlled with high precision. As disclosed in, forexample, Japanese Patent Laid-Open Publication No. 2002-141012, error ofthe feed amount of the horizontally traveling stage 1110 or the like canbe detected by laser measurement, etc. so as to be eliminated by drivingthe electrode 1106.

In the conventional electron beam recorder, even if mechanicalaccuracies such as the feed amount of the horizontally traveling stage1111 and the nonrepeatable runout of the rotary stage 1110 can becorrected, position of the electron beam 1120 itself is quite likely tovary and thus, it is of vital importance to correct variations of theposition of the electron beam 1120. The variations of the position ofthe electron beam 1120 result from great influences such as variationsof magnetic field around the recorder, mechanical vibrations, acousticnoise and electrical noise of the recorder, etc. which are exerted onthe electron beam 1120.

Generally, since the electron beam source 1101 and the electron opticalsystem 1102 are accommodated in the vacuum chamber 1113, it is quitedifficult to detect the variations of the position of the electron beam1120 accelerated and converged in the vacuum chamber 1113. Meanwhile, amethod may be considered in which the electron beam 1120 used forrecording is irradiated on a detection object different from the master1109, for example, the focusing grid 1112 and variations of irradiationposition of the electron beam 1120 are detected by using signals of adetector for detecting an image formed on the detection object. However,this method cannot be used when signals are being recorded on the master1109. Thus, even in this method, it is extremely difficult to detect andcorrect variations of the position of the electron beam 1120 when thesignals are being recorded on the master 1109.

SUMMARY OF THE INVENTION

Accordingly, an essential object of the present invention is to raise,with a view to eliminating the above mentioned drawbacks of prior art,accuracy of a track pitch of an information recording medium bydetecting and correcting variations of irradiation position of anelectron beam during recording on a master of the information recordingmedium.

To this end, the present invention proposes an electron beam recorder inwhich an electron beam irradiation position detecting unit for detectinga quantity of an electron beam shielded partially at the time ofdeflection of an optical axis of the electron beam so as to be capableof detecting position of the electron beam while the electron beam isbeing irradiated on the master is provided in an electron optical systemsuch that variations of the position of the electron beam can becorrected highly accurately also during recording.

In order to accomplish this end, an electron beam recorder of thepresent invention includes an electron optical system for irradiating anelectron beam on a master of an information recording medium. Anelectron beam irradiation position detecting unit detects an irradiationposition of the electron beam in the electron optical system while theelectron beam is being irradiated on the master by the electron opticalsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

This object and features of the present invention will become apparentfrom the following description taken in conjunction with the preferredembodiments thereof with reference to the accompanying drawings inwhich:

FIG. 1 is a schematic sectional view showing an arrangement of anelectron beam recorder according to a first embodiment of the presentinvention;

FIG. 2 is a top plan view showing an arrangement of an electron beamirradiation position detecting unit of the electron beam recorder ofFIG. 1;

FIG. 3 is a top plan view showing relative positions of electrodes, ashielding plate and the electron beam irradiation position detectingunit of FIG. 2 in the electron beam recorder of FIG. 1;

FIGS. 4A, 4B and 4C are top plan views showing a normal position anddeflections of an electron beam in the electron beam irradiationposition detecting unit of FIG. 2;

FIG. 5 is a graph showing relation between electron beam irradiationposition and output of the electron beam irradiation position detectingunit of FIG. 2 in the electron beam recorder of FIG. 1;

FIG. 6 is a schematic sectional view showing an arrangement of anelectron beam recorder which is a modification of the electron beamrecorder of FIG. 1;

FIG. 7 is a schematic sectional view showing an arrangement of anelectron beam recorder according to a second embodiment of the presentinvention;

FIG. 8 is a top plan view showing an arrangement of an electron beamirradiation position detecting unit of the electron beam recorder ofFIG. 7;

FIG. 9 is a schematic sectional view showing another example of layoutof the electron beam irradiation position detecting unit of FIG. 8 inthe electron beam recorder of FIG. 7;

FIG. 10 is a schematic sectional view showing an arrangement of anelectron beam recorder according to a third embodiment of the presentinvention;

FIG. 11 is a diagram showing positional relation between an electronbeam and two magnetic field sensors employed in an electron beamirradiation position detecting unit of the electron beam recorder ofFIG. 10;

FIG. 12 is a schematic sectional view showing an arrangement of anelectron beam recorder according to a fourth embodiment of the presentinvention;

FIG. 13 is a schematic sectional view showing an arrangement of anelectron beam irradiation position detecting unit of the electron beamrecorder of FIG. 12;

FIG. 14 is a schematic sectional view showing an arrangement of anelectron beam recorder according to a fifth embodiment of the presentinvention; and

FIG. 15 is a schematic sectional view showing an arrangement of a priorart electron beam recorder.

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout several views of the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention are described withreference to the drawings.

First Embodiment

FIG. 1 shows an arrangement of an electron beam recorder for recordingsignals on a master 109 of an information recording medium, for example,an optical disc by using an electron beam 120, according to a firstembodiment of the present invention. This electron beam recorder has afollowing arrangement portion similar to that of a conventional electronbeam recorder of FIG. 15. Namely, this electron beam recorder includesan electron beam source 101 for generating an electron beam 120 and anelectron optical system 102 which converges the emitted electron beam120 onto the resist master 109 so as to record information patterns onthe resist master 109 in accordance with inputted information signals.The electron beam source 101 and the electron optical system 102 areaccommodated in a vacuum chamber 113.

The electron beam source 101 is constituted by a filament for emittingelectrons upon flow of electric current therethrough, an electrode forsuppressing the emitted electrons, an electrode for extracting andaccelerating the electron beam 120, etc. and is adapted to emit theelectrons from one point.

Meanwhile, the electron optical system 102 includes a lens 103 forconverging the electron beam 120, an aperture 104 for determining a beamdiameter of the electron beam 120, electrodes 105 and 106 for deflectingthe electron beam 120 in orthogonal directions, respectively inaccordance with the inputted information signals, a shielding plate 107for shielding the electron beam 120 bent by the electrode 105 and a lens108 for converging the electron beam 120 onto a surface of the resistmaster 109.

Furthermore, the resist master 109 is held on a rotary stage 110 and ismoved horizontally together with the rotary stage 110 by a horizontallytraveling stage 111. If the master 109 is moved horizontally by thehorizontally traveling stage 111 while being rotated by the rotary stage110, the electron beam 120 can be irradiated spirally on the master 109so as to record the information signals of the optical disc spirally onthe master 109.

Moreover, a focusing grid 112 is provided so as to be substantiallyflush with the surface of the master 109. This focusing grid 112 isprovided for adjusting a focal position of the lens 108 such that thelens 108 converges the electron beam 120 onto the surface of the master109. If electrons reflected by the focusing grid 112 or secondaryelectrons emitted from the focusing grid 120 upon irradiation of theelectron beam 120 on the focusing grid 112 are detected by a detectorsuch that a grid image is monitored, the focal position of the lens 108can be adjusted from a state in which the grid image is seen.

In the present invention, an electron beam irradiation positiondetecting unit 114 for detecting a position of the electron beam 120passing therethrough is provided in the electron optical system 102 andbelow the lens 108 in addition to the above mentioned arrangementportion similar to that of the conventional electron beam recorder ofFIG. 15. This electron beam irradiation position detecting unit 114 isarranged as follows. FIG. 2 is a top plan view of the electron beamirradiation position detecting unit 114 as observed from the electronbeam source 101. In the electron beam irradiation position detectingunit 114 shown in FIG. 2, shielding plates 121 and 122 are,respectively, provided at opposite sides of the electron beam 120passing through the electron beam irradiation position detecting unit114. The shielding plates 121 and 122 have, respectively, linear edges121 a and 122 a extending in a direction substantially perpendicular toa feed direction X of the horizontally traveling stage 111, namely, in arotational direction Y of the master 109. The shielding plates 121 and122 are provided such that the respective edges 121 a and 122 a aresubstantially brought into contact with the electron beam 120.

Meanwhile, electron beam detectors 123 and 124 are, respectively,connected to the shielding plates 121 and 122 so as to output signals aand b proportional to quantities of the electron beam 120 irradiated onthe shielding plates 121 and 122, respectively. Thus, when the electronbeam 120 has been deflected in the feed direction X of the horizontallytraveling stage 111 due to variations of ambient magnetic field ormechanical vibrations and electrical noise of the electron beamrecorder, a portion of the electron beam 120 is irradiated on theshielding plate 121 or 122, so that the signals a and b corresponding tothe quantities of the electron beam 120 irradiated on the shieldingplates 121 and 122 are, respectively, outputted from the electron beamdetectors 123 and 124 provided for the shielding plates 121 and 122,respectively.

FIG. 3 illustrates relative positions of the electrodes 105 and 106, theshielding plate 107 and the electron beam irradiation position detectingunit 114. As shown in FIG. 3, the electrode 105 is formed by a pair ofelectrode portions interposing the electron beam 120 therebetween and isprovided so as to bend the electron beam 120 in the directionsubstantially perpendicular to the feed direction X of the horizontallytraveling stage 111, i.e., in the rotational direction Y of the master109. The electrode 105 is capable of bending the electron beam 120towards the shielding plate 107 in accordance with signals inputted tothe electrode 105 so as to select whether or not the electron beam 120is irradiated on the master 109 such that information pit patterns arerecorded on the master 109.

Meanwhile, in FIG. 3, the electrode 106 is formed by a pair of electrodeportions interposing the electron beam 120 therebetween and is providedfor bending the electron beam 120 in a direction substantiallyperpendicular to that of the electrode 105, i.e., in the substantiallysame direction as the feed direction X of the horizontally travelingstage 111 and is capable of bending the electron beam 120 in thesubstantially same direction as the feed direction X of the horizontallytraveling stage 111 in accordance with signals inputted to the electrode106. Since the feed direction X of the horizontally traveling stage 111corresponds to a radial direction of the master 109 to be recorded,variations of a track pitch of the optical disc, etc. can be correctedby the signals inputted to the electrode 106.

FIGS. 4A, 4B and 4C show a normal position and deflections of theelectron beam 120 in the electron beam irradiation position detectingunit 114. In FIG. 4A showing the normal position of the electron beam120, the shielding plates 121 and 122 are provided such that the edges121 a and 122 a of the shielding plates 121 and 122 are substantiallybrought into contact with the electron beam 120. When the electron beamdetectors 123 and 124 have outputted the signals a and b, respectivelyas described above, a signal (b-a) varies as shown in FIG. 5 when anirradiation position of the electron beam 120 is deflected. FIG. 5 showsrelation between the irradiation position of the electron beam 120 andthe signal (b-a). For example, in FIG. 4A showing the normal position ofthe electron beam 120, since the irradiation position of the electronbeam 120 is disposed at a center between the shielding plates 121 and122 and the electron beam 120 is not shielded by both of the shieldingplates 121 and 122, the output signals a and b from the electron beamdetectors 123 and 124 assume zero substantially, so that the signal(b-a) assumes zero substantially as indicated by an origin O in FIG. 5.

On the other hand, in case the irradiation position of the electron beam120 has been deflected from the normal position of FIG. 4A towards theshielding plate 122 in the direction of the arrow A as shown in FIG. 4B,the electron beam detector 124 provided on the shielding plate 122outputs the signal b proportional to the quantity of the electron beam120 shielded by the shielding plate 122, while the output signal a fromthe electron beam detector 123 provided on the shielding plate 121assumes zero. Thus, the signal (b-a) shifts to a plus domain asindicated by a curve 131 in FIG. 5. On the contrary, in case theirradiation position of the electron beam 120 has been deflected fromthe normal position of FIG. 4A towards the shielding plate 121 in thedirection of the arrow B as shown in FIG. 4C, the electron beam detector123 provided on the shielding plate 121 outputs the signal aproportional to the quantity of the electron beam 120 shielded by theshielding plate 121, while the output signal b from the electron beamdetector 124 provided on the shielding plate 122 assumes zero. Thus, thesignal (b-a) shifts to a minus domain as indicated by a curve 132 inFIG. 5. Therefore, the position of the electron beam 120 can be detectedfrom the values of the signal (b-a).

Meanwhile, the electron beam 120 having passed through the electron beamirradiation position detecting unit 114 without being shielded by theshielding plates 121 and 122 is irradiated on the master 109 so as torecord the signals on the master. Accordingly, by using the electronbeam irradiation position detecting unit 114, it is possible to detectvariations of the position of the electron beam 120 in the electronoptical system 102 while the electron beam 120 is being irradiated onthe master 109 by the electron optical system 102.

Since variations of the track pitch recorded on the master 109 of theoptical disc can be monitored by using the electron beam irradiationposition detecting unit 114, it is possible as follows to judge, duringrecording, whether or not the variations of the track pitch recorded onthe master 109 fall within a permissible range. For example, prior torecording on the master 109, the electron beam 120 is initiallydisplaced greatly in the feed direction X of the horizontally travelingstage 111 by an electron beam deflecting member, e.g., the electrode 106and a sample is recorded on a test master or the like while its changeof the position of the electron beam 120 is being confirmed by theelectron beam irradiation position detecting unit 114. By inspecting ashape of the recorded sample with an electron microscope or the like,correlation between amount of the change of the irradiation position ofthe electron beam 120 and the output signal of the electron beamirradiation position detecting unit 114 is grasped preliminarily. Here,the position of the electron beam 120 is varied greatly such that theamount of the change of the irradiation position of the electron beam120 can be obtained from the shape of the recorded sample.

Supposing that the track pitch recorded on the master 109 is 0.32 μm anda permissible variation of the track pitch for the optical disc is ±5nm, it is possible to beforehand convert, from results of recording onthe test master, the output signal of the electron beam irradiationposition detecting unit 114 obtained at the time the variations of thetrack pitch fall within the permissible range of ±5 nm. Thus, if theoutput signal of the electron beam irradiation position detecting unit114 is monitored continuously during actual recording of the master 109of the optical disc, it is possible to estimate whether or not thevariations of the track pitch of the master 109 fall within thepermissible range.

In the first embodiment, the electron beam irradiation positiondetecting unit 114 is provided in the electron optical system 102 andbelow the lens 108. Namely, in the electron optical system 102, theelectron beam irradiation position detecting unit 114 is disposed at alocation closest to the master 109. However, the electron beamirradiation position detecting unit 114 may also be provided at anotherlocation in the electron optical system 102. Nevertheless, in case theelectron beam irradiation position detecting unit 114 monitorsvariations of radial position of the patterns recorded on the master109, it is preferable that the electron beam irradiation positiondetecting unit 114 is disposed as close to the master 109 as possible.

Meanwhile, in the first embodiment, the edges 121 a and 122 a of theshielding plates 121 and 122 of the electron beam irradiation positiondetecting unit 114 are formed into a linear shape but may also haveother shapes than the linear shape, e.g., a circular shape effectively.

Meanwhile, FIG. 6 shows an electron beam recorder which is amodification of the electron beam recorder of FIG. 1. This modifiedelectron beam recorder includes a positional information control device140 connected between the electron beam irradiation position detectingunit 114 and the electrode 106. By employing this arrangement of theelectron beam recorder of FIG. 6, variations of the irradiation positionof the electron beam 120 are restrained such that nonuniform feed of thepatterns recorded on the master 109 can be lessened. As shown in FIG. 5,when there is no variation of the irradiation position of the electronbeam 120, the zero-signal 0 indicated by the origin O is outputted asthe electron beam irradiation position signal (b-a). When the electronbeam 120 has been displaced towards the shielding plate 122, the plussignal 131 is outputted as the signal (b-a). On the contrary, when theelectron beam 120 has been displaced towards the shielding plate 121,the minus signal 132 is outputted as the signal (b-a).

This signal (b-a) is inputted to the positional information controldevice 140 so as to be subjected to predetermined signal amplificationor signal attenuation in the positional information control device 40and then, is fed back to the deflection electrode 106. The deflectionelectrode 106 is capable of bending the electron beam 120 in thesubstantially same direction as the feed direction X of the horizontallytraveling stage 111. Thus, if the electrode 106 bends, by using theelectron beam positional variation information detected by the electronbeam irradiation position detecting unit 114, the electron beam 120 in adirection for reducing positional variations of the electron beam 120,the irradiation position of the electron beam 120 can be stabilized. Bythis arrangement of the electron beam recorder of FIG. 6, variations ofthe optical disc track pitch recorded on the master 109, etc. can becorrected.

Second Embodiment

FIG. 7 shows an arrangement of an electron beam recorder according to asecond embodiment of the present invention. In the electron beamrecorder of the second embodiment, the aperture 104 of the electron beamrecorder of the first embodiment is eliminated and the electron beamirradiation position detecting unit 114 of the electron beam recorder ofthe first embodiment is replaced by an electron beam irradiationposition detecting unit 214. Since other constructions of the electronbeam recorder of the second embodiment are similar to those of theelectron beam recorder of the first embodiment, the description isabbreviated for the sake of brevity. As shown in FIG. 8, the electronbeam irradiation position detecting unit 214 includes a shielding plate222 and a hole 221 for determining a beam diameter of the electron beam120 is provided at a center of the shielding plate 222 in the feeddirection X of the horizontally traveling stage 111 and the rotationaldirection Y of the master 109.

When the electron beam 120 having the beam diameter larger than adiameter of the hole 221 is passed through the hole 221, an outerperipheral portion of the electron beam 120 is shielded by the shieldingplate 222 such that the beam diameter of the electron beam 120 havingpassed through the hole 221 is determined. Meanwhile, the shieldingplate 222 is bisected into a first region 222 a and a second region 222b at the hole 221 in a direction substantially perpendicular to the feeddirection X of the horizontally traveling stage 111 and electron beamdetectors 223 and 224 are, respectively, connected to the first andsecond regions 222 a and 222 b so as to output signals a and bcorresponding to quantities of the electron beam 120 irradiated on thefirst and second regions 222 a and 222 b, respectively.

Edges of the first and second regions 222 a and 222 b of the shieldingplate 222, which surround the hole 221, have contours substantiallyidentical with those of edges of the hole 221. When the electron beam120 flowing through the hole 221 has been deflected towards the secondregion 222 b, the signal (b-a) shifts to the plus domain as indicated bythe curve 131 in FIG. 5. On the contrary, when the electron beam 120flowing through the hole 221 has been deflected towards the first region222 a, the signal (b-a) shifts to the minus domain as indicated by thecurve 132 in FIG. 5. When the output signals a and b from the electronbeam detectors 223 and 224 have a substantially identical intensity, thesignal (b-a) assumes zero substantially. Namely, by detecting the signal(b-a), position of the electron beam 120 irradiated on the electron beamirradiation position detecting unit 214 can be detected.

In the second embodiment, the hole 221 is formed into a circular shapebut may also have other shapes than the circular shape, for example, asquare, a rectangle and an ellipse.

Meanwhile, in the second embodiment, the electron beam irradiationposition detecting unit 214 is provided, in the electron optical system102, at a location closest to the master 109 but may also be disposed atany location in the electron optical system 102, for example, betweenthe lens 103 and the electrode 105 as shown in FIG. 9. However, usually,it is preferable that the electron beam irradiation position detectingunit 214 is disposed as close to the master 109 as possible.

Since variations of the track pitch recorded on the master 109 of theoptical disc can be monitored by using the electron beam irradiationposition detecting unit 214, it is possible to judge, during recording,whether or not the variations of the track pitch recorded on the master109 fall within a permissible range.

Meanwhile, if the electron beam irradiation position signal (b-a)outputted by the electron beam irradiation position detecting unit 214is fed back to the deflection electrode 106 capable of bending theelectron beam 120 in the feed direction X of the horizontally travelingstage 111, variations of the irradiation position of the electron beam120 can be restrained.

Third Embodiment

FIG. 10 shows an arrangement of an electron beam recorder according to athird embodiment of the present invention. In the electron beam recorderof the third embodiment, the electron beam irradiation positiondetecting unit 114 of the electron beam recorder of the first embodimentis replaced by an electron beam irradiation position detecting unit 314.Since other constructions of the electron beam recorder of the thirdembodiment are similar to those of the electron beam recorder of thefirst embodiment, the description is abbreviated for the sake ofbrevity. The electron beam irradiation position detecting unit 314includes magnetic field sensors 315 and 316 for detecting intensity ofmagnetic field generated about a central axis located at an optical axisof the electron beam 120 in the electron optical system 102. Themagnetic field sensors 315 and 316 each formed by a coil are spaced asubstantially identical distance from the optical axis of the electronbeam 120 and confront each other in the feed direction X of thehorizontally traveling stage 111 so as to have the optical axis of theelectron beam 120 as a center therebetween.

The intensity of the magnetic field generated by the electron beam 120running between the magnetic field sensors 315 and 316 is determined bya distance from the optical axis of the electron beam 120. As a distancefrom the optical axis of the electron beam 120 to the magnetic fieldincreases, the intensity of the magnetic field decreases. Thus, in casethe electron beam 120 passes through a substantially central positionbetween the magnetic field sensors 315 and 316, a quantity of electriccurrent flowing through the magnetic field sensor 315 becomessubstantially identical with that of the magnetic field sensor 316.However, if the electron beam 120 is deflected from the central positionbetween the magnetic field sensors 315 and 316, the quantity of electriccurrent flowing through the magnetic field sensor 315 becomes differentfrom that of the magnetic field sensor 316.

FIG. 11 shows positional relation between the electron beam 120 and themagnetic field sensors 315 and 316. The magnetic field sensors 315 and316 are disposed symmetrically with respect to a position 321 of theelectron beam 120 as a center therebetween. In case the electron beam120 flows at the position 321, quantities of electric current generatedin the magnetic field sensors 315 and 316 are set to be substantiallyidentical with each other. Thus, if the electron beam 120 has beendeflected from the position 321 to a position 322, the magnetic fieldsensor 315 comes closer to the electron beam 120, while the magneticfiled sensor 316 lies farther from the electron beam 120. The magneticfield generated by the electron beam 120 is inversely proportional to adistance from the electron beam 120. Thus, a quantity of electriccurrent generated in the magnetic field sensor 315 becomes larger thanthat of the magnetic field sensor 316. On the contrary, if the electronbeam 120 has been deflected from the position 321 to a position 323, thequantity of electric current generated in the magnetic field sensor 315becomes smaller than that of the magnetic field sensor 316. Namely, bymonitoring the quantities of electric current outputted from themagnetic field sensors 315 and 316, it is possible to detect position ofthe optical axis of the electron beam 120 flowing between the magneticfield sensors 315 and 316.

As described above, the two magnetic field sensors 315 and 316 areprovided as the electron beam irradiation position detecting unit 314 soas to be disposed symmetrically with respect the optical axis of theelectron beam 120. Thus, even if a quantity of the electron beam 120 haschanged, it is possible to detect a deviation of the electron beam 120from the central position 321 by taking a difference signal of outputsof the magnetic field sensors 315 and 316.

Here, the two magnetic field sensors 315 and 316 are disposedsymmetrically with respect to the optical axis of the electron beam 120.However, in case the magnetic field sensors 315 and 316 are provided atlocations passing through the optical axis of the electron beam 120 andlying in parallel with the feed direction X of the horizontallytraveling stage 111, the magnetic field sensors 315 and 316 are capableof detecting position of the electron beam 120 even if the magneticfiled sensors 315 and 316 are not spaced an identical distance from theoptical axis of the electron beam 120. Meanwhile, even a single magneticfield sensor is capable of detecting position of the electron beam 120.

In the third embodiment, each of the magnetic field sensors 315 and 316is formed by the coil but a sensor capable of detecting variations ofthe magnetic field may also achieve the same effect as the coil.

Since variations of the track pitch recorded on the master 109 of theoptical disc can be monitored by using the electron beam irradiationposition detecting unit 314, it is possible to judge, during recording,whether or not the variations of the track pitch recorded on the master109 fall within a permissible range.

Meanwhile, if an electron beam irradiation position signal outputted bythe electron beam irradiation position detecting unit 314 is fed back tothe deflection electrode 106 capable of bending the electron beam 120 inthe feed direction X of the horizontally traveling stage 111, variationsof the irradiation position of the electron beam 120 can be restrained.

Fourth Embodiment

FIG. 12 shows an arrangement of an electron beam recorder according to afourth embodiment of the present invention. In the electron beamrecorder of the fourth embodiment, the electron beam irradiationposition detecting unit 114 of the electron beam recorder of the firstembodiment is replaced by an electron beam irradiation positiondetecting unit 414. Since other constructions of the electron beamrecorder of the fourth embodiment are similar to those of the electronbeam recorder of the first embodiment, the description is abbreviatedfor the sake of brevity. As shown in FIG. 13, the electron beamirradiation position detecting unit 414 includes shielding plates 421and 422 which confront each other in the feed direction X of thehorizontally traveling stage 111 so as to have the optical axis of theelectron beam 120 in the electron optical system 102 as a centertherebetween and are substantially brought into contact with theelectron beam 120, luminescent layers 423 and 424 made of, for example,fluorescent substance, which emit light upon irradiation of the electronbeam 120 thereon and are, respectively, coated on the shielding plates421 and 422 and photosensors 425 and 426 for detecting intensities oflight emitted from the luminescent layers 423 and 424, respectively,which are disposed above the shielding plates 421 and 422 so as to bedirected towards the fluorescent layers 423 and 424, respectively.

The shielding plates 421 and 422 have, respectively, edges 421 a and 422a extending in a direction substantially perpendicular to the feeddirection X of the horizontally traveling stage 111. The shieldingplates 421 and 422 are provided in the feed direction X of thehorizontally traveling stage 111 such that the respective edges 421 aand 422 a are substantially brought into contact with the electron beam120 passing through the electron beam irradiation position detectingunit 414.

When the electron beam 120 has been deflected in the feed direction X ofthe horizontally traveling stage 111 due to variations of ambientmagnetic field or mechanical vibrations and electrical noise of theelectron beam recorder, a portion of the electron beam 120 is irradiatedon the shielding plate 421 or 422, so that light is emitted from theluminescent layer 423 or 424 coated on the shielding plate 421 or 422.By detecting a quantity of the emitted light with the photosensor 425 or426, it is possible to detect a direction and an amount of deflection ofthe electron beam 120.

Meanwhile, in the fourth embodiment, the electron beam irradiationposition detecting unit 414 is provided, in the electron optical system102, at a location closest to the master 109 but may also be disposed atanother location in the electron optical system 102. However, usually,it is preferable that the electron beam irradiation position detectingunit 414 is disposed as close to the master 109 as possible.

Since variations of the track pitch recorded on the master 109 of theoptical disc can be monitored by using the electron beam irradiationposition detecting unit 414, it is possible to judge, during recording,whether or not the variations of the track pitch recorded on the master109 fall within a permissible range.

Meanwhile, if an electron beam irradiation position signal outputted bythe electron beam irradiation position detecting unit 414 is fed back tothe deflection electrode 106 capable of bending the electron beam 120 inthe feed direction X of the horizontally traveling stage 111, variationsof the irradiation position of the electron beam 120 can be restrained.

Fifth Embodiment

FIG. 14 shows an arrangement of an electron beam recorder according to afifth embodiment of the present invention. In the electron beam recorderof the fifth embodiment, the aperture 104 and the electron beamirradiation position detecting unit 114 of the electron beam recorder ofthe first embodiment are, respectively, replaced by an aperture 504 andan electron beam irradiation position detecting unit 514. In contrastwith the electron beam irradiation position detecting unit 114 providedbelow the lens 108 in the electron beam recorder of the firstembodiment, the electron beam irradiation position detecting unit 514 isdisposed immediately below the aperture 504. Since other constructionsof the electron beam recorder of the fifth embodiment are similar tothose of the electron beam recorder of the first embodiment, thedescription is abbreviated for the sake of brevity. As shown in FIG. 14,the aperture 504 has holes 504 a and 504 b for bifurcating the electronbeam 120 from the electron beam source 101 into a main electron beamportion 120A and a branch electron beam portion 120B, respectively. Themain electron beam portion 120A is passed through the electron opticalsystem 102 as it is and is irradiated on the master 109 so as to recordpatterns on the master 109, while the branch electron beam portion 120Bis inputted to the electron beam irradiation position detecting unit514.

Any one of the electron beam irradiation position detecting unit 114 ofthe first embodiment, the electron beam irradiation position detectingunit 214 of the second embodiment and the electron beam irradiationposition detecting unit 414 of the fourth embodiment may be used as theelectron beam irradiation position detecting unit 514.

In the electron beam recorder of the above described arrangement, incase the main electron beam portion 120A used for recording is deflectedby variations of external magnetic field or mechanical vibrations, thebranch electron beam portion 120B may also be deflected likewise. Thus,if correlation between positional variations of the main electron beamportion 120A and those of the branch electron beam portion 120B is takenprior to recording of the patterns on the master 109, it becomespossible to detect variations of the irradiation position of theelectron beam 120 while the patterns are being recorded on the master109 by the electron beam 120.

Since variations of the track pitch recorded on the master 109 of theoptical disc can be monitored by using the electron beam irradiationposition detecting unit 514, it is possible to judge, during recording,whether or not the variations of the track pitch recorded on the master109 fall within a permissible range.

Meanwhile, if an electron beam irradiation position signal outputted bythe electron beam irradiation position detecting unit 514 is fed back tothe deflection electrode 106 capable of bending the electron beam 120 inthe feed direction X of the horizontally traveling stage 111, variationsof the irradiation position of the electron beam 120 can be restrained.

As is clear from the foregoing description of the present invention, byusing the electron beam irradiation position detecting unit, variationsof the irradiation position of the electron beam can be detected whilethe electron beam is being irradiated on the master so as to record thepatterns on the master. Thus, during recording on the master, it ispossible to judge whether or not the variations of the track pitchrecorded on the master fall within the permissible range. Meanwhile, bydriving the deflection electrode by using the signal of the electronbeam irradiation position detecting unit, it becomes possible torestrain the variations of the track pitch recorded on the master.

1. An electron beam recorder comprising: an electron optical system forirradiating an electron beam on a master of an information recordingmedium; and an electron beam irradiation position detecting unit fordetecting an irradiation position of the electron beam in the electronoptical system while the electron beam is being irradiated on the masterby the electron optical system, the electron beam irradiation positiondetecting unit including: a shielding plate for shielding the electronbeam, which has a hole for shaping the electron beam to a desired beamdiameter and is divided, at the hole, into first and second regions in adirection substantially perpendicular to a horizontal feed direction ofthe master; and first and second electron beam detectors for detecting,as first and second detection signals, quantities of the electron beamshielded by the first and second regions of the shielding plate,respectively such that a difference signal of the first and seconddetection signals is obtained.
 2. A method of detecting, in an electronbeam recorder for recording signals on a master of an informationrecording medium by an electron beam, an irradiation position of theelectron beam, comprising the steps of: irradiating the electron beam onthe master so as to record information on the master; shielding theirradiated electron beam with a shielding plate which is divided intofirst and second regions detecting quantities of the electron beamshielded by the first and second regions of the shielding plate; andgenerating first and second detection signals based on the quantities ofthe election beam shielded by the first and second regions of theshielding plate, respectively, such that the position of the electronbeam is detected by a difference signal of the first and seconddetection signals.